In internal combustion engines, fuel and air are introduced into cylinders for combustion. Pistons move within the cylinders under the influence of a crankshaft located in a crankcase. In each cylinder, a piston compresses the fuel and air mixture prior to combustion of the mixture. Combustion then drives the pistons and yields power output, which may drive a machine.
Combustion in the cylinder releases energy and generates combustion products and by-products, most of which are exhausted from the cylinder into an exhaust system of the engine during the exhaust phase of the combustion cycle. However, some of the combustion products may enter into the crankcase by blowing past seal rings around the pistons, and are thus termed “blow-by gases” or simply “blow-by.” Blow-by gases contain contaminants normally found in exhaust gases, such as, for example, hydrocarbons (HC), carbon monoxide (CO), nitric oxides (NOX), soot, and unburned or partially burned fuel. In addition, because the crankcase is partially filled with lubricating oil being agitated at high temperatures, the blow-by gases may also contain oil droplets and oil vapor. Lubricating oil in the crankcase tends to be atomized or otherwise entrained in the hot blow-by gases to form what may be termed an aerosol.
It may be desirable to vent blow-by gases in the crankcase (including, for example, entrained lubricating oil) as crankcase emissions to relieve pressure in the crankcase. The crankcase emissions may be vented to an air intake side of the engine for mixing with air and fuel introduced into the cylinders, with such systems generally identified as closed crankcase ventilation (CCV) systems, or alternatively the crankcase emissions may be vented to an exhaust system for treatment prior to release to the environment.
Some engines, such as large diesel engines, for example, utilize forced induction to enhance the power output of the engine. This may involve the use of superchargers or turbochargers in an engine design assembly. Returning crankcase emissions to the air intake side of engine, such as via a compressor in a supercharger or turbocharger, can result in fouling of the components (e.g., the compressor wheel) in a relatively short time period. One effect of reintroducing blow-by gases into an intake air of an engine may include producing contaminant buildup (e.g., oil coatings and sludge), within engine components including, for example, turbochargers and cooling devices such as air-to-air aftercoolers (ATAAC). Contaminants, such as those left by blow-by gases, within engine sub-components can negatively affect, for example, power production of the engine and possibly reduce the operational life thereof. The fouling may be further compounded in systems which, for example, utilize multiple turbocharger systems, as the heat increases in downstream compressor units. Again, other components, such as cooling units downstream of a supercharger or turbocharger, may be fouled. Even with the development of technologies to address purifying crankcase emissions before being returned to the intake system, some level of contamination may still exist that may be harmful to engine components, such as a supercharger or turbocharger, cooling units, or various other engine intake system components.
U.S. Patent Application Publication No. US 2007/0251512 A1 by Wallington (“Wallington”) discloses an integrated check valve breather assembly for venting blow-by gases from a crankcase. The check valve includes a reed valve element that automatically actuates to an open position to vent crankcase emissions when the crankcase pressure reaches a threshold. When the check valve is open, gases from the crankcase are vented to an exhaust system, which may include a diesel particulate filter (DPF) and regeneration system. Because the blow-by gases are not recirculated to the engine air intake, the engine and associated components are protected from contact with the blow-by gases.
While the breather assembly of Wallington addresses the above-noted deleterious effects of blow-by gases, the check valve disclosed in Wallington is subject to premature wear. More specifically, during machine operation, the reed valve element would impact the valve set and valve stop with excessive force as it closed and opened, respectively. This not only hastened structural deterioration of the valve element, but also would generate pressure oscillations that could cause the valve element to vibrate against the valve seat, causing additional wear. When the reed valve element fails, blow-by gases and oil from the crankcase are allowed to flow through the CCV and into the DPF and regeneration system. The oil content of the blow-by gases would cause more frequent DPF regeneration events, which may cause premature failure of the DPF.